FIX: overflow when idx larger than count

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6944 8aca7d54-2c30-db11-9de9-000461428c89
FIX: brueckenabuer can now again do crossings if needed

git-svn-id: svn://tron.homeunix.org/simutrans/simutrans/trunk@6945 8aca7d54-2c30-db11-9de9-000461428c89